The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Wireless network devices such as client stations operate in an ad-hoc mode or an infrastructure mode as shown in FIGS. 1 and 2, respectively. In the ad-hoc mode, each client station 10-1, 10-2, . . . , and 10-N (collectively client stations 10) communicates directly with other client stations without requiring an access point (AP). In the infrastructure mode, each client station 20-1, 20-2, . . . , and 20-M (collectively client stations 20) communicates with other client stations through an AP 24. The AP 24 may provide a connection to a network 26, a server 28, and/or Internet 30.
Referring now to FIG. 3, the AP 24 transmits beacons at a beacon interval. Every Nth beacon is a delivery traffic indication message (DTIM) beacon, where N is an integer greater than or equal to 1. The DTIM beacon is followed by buffered broadcast and multicast frames transmitted by the AP 24 to the client stations 20.
Generally, the AP 24 and the client stations 20 do not exchange data after each DTIM beacon. Accordingly, client stations 20 may operate in two modes: an active mode and an inactive (or sleep) mode. When the AP 24 and the client stations 20 exchange data, the client stations 20 may operate in the active mode. On the other hand, when the AP 24 and the client stations 20 do not exchange data, the client stations 20 may operate in the inactive mode to conserve power. Components of the client station are shut down during the inactive mode. An inactive mode clock and a wake up module determine when to transition back to the active mode. Based on the DTIM beacon interval, the client stations 20 may determine the amount of time to remain in the inactive mode before waking up to receive the next DTIM beacon.